WASHINGTON (Reuters) - A large star in its death throes is leaving a huge, turbulent tail of oxygen, carbon and nitrogen in its wake that makes it look like an immense comet hurtling through space, astronomers said on Wednesday.

Nothing like this has ever previously been witnessed in a star, according to scientists who detected it using NASA's Galaxy Evolution Explorer, an orbiting space telescope that observes the cosmos in ultraviolet light.

This tail, spanning a stunning distance of 13 light-years, was detected behind the star Mira, located 350 light-years from Earth in the "whale" constellation Cetus.

"There's a star with a tail in the tail of the whale," said one of the researchers, astronomer Mark Seibert of the Observatories of the Carnegie Institution of Washington in Pasadena, California.

A light year is about 6 trillion miles, the distance light travels in a year.

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Rocketing through our Milky Way galaxy at 80 miles per second (130 km per second) -- literally faster than a speeding bullet -- the star is spewing material that scientists believe may be recycled into new stars, planets and maybe even life.

"We believe that the tail is made up of material that is being shed by the star which is heating up and then spiraling back into this turbulent wake," said astronomer Christopher Martin of California Institute of Technology, one of the researchers in the study published in the journal Nature.

Mira is a so-called "red giant" star near the end of its life. Astronomers believe our sun will become a similar red giant in 4 to 5 billion years, but they doubt it will develop such a tail because it is not moving through space as quickly.

'PHOENIX-LIKE REVIVALS'

"It's giving us this fantastic insight into the death processes of stars and their renewals -- their phoenix-like revivals as their ashes get cycled backed into the next generation of stars," added Michael Shara of the American Museum of Natural History and Columbia University in New York.

Shara said he expects that as this telescope continues mapping the cosmos in ultraviolet light for the first time, other similar stars may be discovered. "There must be lots more of these things," Shara said.

NASA images show the tail as a glowing light-blue stream of material including oxygen, carbon and nitrogen.

This material has been blown off Mira gradually over time -- the oldest was released roughly 30,000 years ago as part of a long stellar death process -- and is enough to form at least 3,000 future Earth-sized planets, the scientists said.

The astronomers were surprised to find this unique feature in Mira, a well-known star studied since the 16th century. Mira (pronounced MY-rah) stems from the Latin word for "wonderful."

Despite having about the same mass as the sun, Mira has swollen up to over 400 times the size of the sun, meaning the force of gravity is having a hard time holding it together, Seibert said.

The tail stretching 13 light-years is thousands of times the length of our solar system. The nearest star to Earth, called Proxima Centauri, is located 4 light-years away.

While this star looks like a comet, stars and comets are quite different celestial bodies. Comets in our solar system are relatively small objects made up of rock, dust and ice trailed by a tail of gas and dust.

Unlike our solitary sun, Mira is a so-called binary star traveling through space orbiting a companion believed to be the burnt-out, dead core of a star, known as a white dwarf.

Scientists think Mira in time will eject all its gas, leaving a colorful shell known as a planetary nebula that also gradually will fade leaving behind a white dwarf.